1. Field
The present invention relates to a storage apparatus.
2. Description of the Related Art
A resistance variation type memory (an FeRAM, an MRAM, a PRAM or an ReRAM) has been known as a (nonvolatile) semiconductor memory capable of holding stored contents also when a power is not supplied.
Each memory cell of the resistance variation type memory is constituted by a storage element in which a resistance value is varied depending on a logical value (“1” or “0”) which is stored. The logical value stored in each memory cell is discriminated corresponding to a magnitude of a current flowing to the storage element.
As means for once blocking the supply of the power and then restarting the same supply, and thereafter carrying out a return at a high speed in the resistance variation type memory, a technique for combining each storage element of the resistance variation type memory with a flip flop has been proposed (for example, JP-A 2008-85570 (KOKAI). JP-A 2008-85570 (KOKAI) has disclosed a method of combining an MTJ element with a flip flop to constitute a nonvolatile flip flop.
In a conventional resistance variation type memory, a logical value of each memory cell is discriminated depending on a magnitude of a current flowing to a storage element. For this reason, there is a disadvantage in that it is necessary to provide, every memory cell, a circuit for converting the current flowing to the storage element into a voltage or a circuit for generating a reference current to be used for discriminating the magnitude of the current flowing to the storage element, resulting in an increase in a circuit scale.